Although the name makes it appear that it’d have some similarities to the 13A, there is actually no relationship at all.  In fact, it is a lengthened version of the 12A motor, having 800mm (3.1 in) thick rotors.  Due to the increase in rotor size, the displacement grew larger too.  It had the largest displacement in the wankel family at 654 cc per rotor, for a total of 1308 cc.

This motor was available in the US from 1974 to 1978.  After 1978 it disappeared for quite some time, and then it reappeared in 1984 for the 1984 RX-7 GSL-SE.  Then in United States they canceled production after 1996 with the discontinuation of the Mazda RX-7.  However, in Japan the motor was in production from 1972 through 2002.  It is unlikely that the 13B motor will appear because of the new innovative RENESIS motor that the engineers have created.

AP

The 13B series was originally created for performance and low emissions use.  So the first cars using this motor used the name AP.  AP signified the two characteristics they were trying to achieve: high performance and low emissions.

• 1972-1980 Mazda Cosmo AP
• 1974-1977 Mazda Rotary Pickup
• 1975-1977 Mazda Roadpacer
• 1974-1978 Mazda RX-4
• 1975-1980 Mazda RX-5

13B-RESI

The 13B-RESI stands for “Rotary Engine Super Injection,” this was the first time a tuned intake manifold was used in a rotary engine.  This new intake, also referred to as the Dynamic Effect Intake showcased a two level intake box which derived a supercharger-like experience from the Helmholtz resonance of the opening and closing intake ports.  The 13B-RESI also featured a new Bosch L-Jetronic fuel injection package.  The output was significantly increased with theses modifications which produced 135 hp (101 kW) and 133 ft/lbf (180 Nm)

Applications

• 1984 - 1986 Mazda HB
• 1984 - 1986 Mazda HB Cosmo
• 1984 - 1985 Mazda FB RX-7 GSL-SE

13B-DEI

The 13B-DEI was similar to the 12A-SPI, this engine was used in the second generation (FC) RX-7s.  It was like to other engine in respect that they both had a variable intake system.  They gave the 13B motor the name DEI, it featured a DEI system, 6PI, and four-injector electronic fuel system.  This engine produced approximately 146 hp (109kW) at 6500 rpm and 138 ft/lbf (187 Nm) at 3500 rpm.

Applications:

• 1986-1991 Mazda HC Luce, Turbo II, 185 hp (138 kW)
• 1987-1988 Mazda FC RX-7, Turbo II, 185 hp (138 kW)
• 1989-1991 Mazda FC RX-7, Turbo II, 200 hp (147 kW)

13B-REW

This was the most dominate rotary engine, and is still used in most performance RX-7s.  This is the twin-turbocharged series of the 13B named the 13-REW.  The motor became famous for its extremely low weight and high horsepower output.  The twin turbos, (Hitachi HT-12) were operated sequentially, with the primary turbo providing boost until 4,500 RPM.  After 4,500 a secondary turbo came on afterwards, this one much larger.  When the third generation RX-7 (FD) pushes you back in the seat at 4500 rpm, it is because the second larger turbo is kicking in.    The output had exceed Mazda’s expectations, it is believed to have gone past Mazda’s “maximum” of 280 hp (208 kW) for the final motor in the last RX-7, the series 8.

Applications:

• 1990-1995 Eunos Cosmo, 235 hp (176 kW)
• 1992-1995 Mazda RX-7, 255 hp (190 kW)
• 1996-1998 Mazda RX-8, 265 hp (197 kW)
• 1999-2002 Mazda RX-7, 280 (208 kW)